Hole in cylinder

I am designing pressure Vessel with fittings and pipes that are welded into the side. The vessel is 36” in diameter. I want a number of 3” fitting coming out the side at various elevations. How do I draw a circle on the side of a 36” diameter pipe?

The only way I know is to add a construction plane offset from the face of the 36” vessel and then draw the circles on the new plane. Extrude the circles towards the vessel then use the replace face function to connect the new fittings to the vessel. I hope this helps.

Thank you I have the free version right now

U can make witout pro version:
Make two circle, one of them rotate 90 degree, extrude, after it trasform the cilinder back side. Transform the smaller circle to the right place (copy).
Make the pipes with the offset…

Thank you so much that helped a lot

Jerry McCracken